Microwave-Assisted Synthesis of NiCo2O4 Double-Shelled Hollow Spheres for High-Performance Sodium Ion Batteries

Nano-Micro Letters, Nov 2017

Xiong Zhang, Yanping Zhou, Bin Luo, Huacheng Zhu, Wei Chu, Kama Huang

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Microwave-Assisted Synthesis of NiCo2O4 Double-Shelled Hollow Spheres for High-Performance Sodium Ion Batteries

Nano-Micro Lett. Microwave-Assisted Synthesis of NiCo2O4 Double-Shelled Hollow Spheres for High-Performance Sodium Ion Batteries Xiong Zhang 0 1 . Yanping Zhou 0 1 . Bin Luo 0 1 . Huacheng Zhu 0 1 . Wei Chu 0 1 . Kama Huang 0 1 0 School of Electronics and Information Engineering, Sichuan University , Chengdu 610065 , People's Republic of China 1 School of Chemical Engineering, Sichuan University , Chengdu 610065 , People's Republic of China The ternary transitional metal oxide NiCo2O4 is a promising anode material for sodium ion batteries due to its high theoretical capacity and superior electrical conductivity. However, its sodium storage capability is severely limited by the sluggish sodiation/desodiation reaction kinetics. Herein, NiCo2O4 double-shelled hollow spheres were synthesized via a microwave-assisted, fast solvothermal synthetic procedure in a mixture of isopropanol and glycerol, followed by annealing. Isopropanol played a vital role in the precipitation of nickel and cobalt, and the shrinkage of the glycerol quasi-emulsion under heat treatment was responsible for the formation of the double-shelled nanostructure. The as-synthesized product NiCo DH glycerol qausiemulsion initial annealing NiCo2O4; Double-shelled hollow sphere; Microwave; Sodium ion battery Highlights NiCo2O4 double-shelled hollow spheres were successfully synthesized via a rapid microwave-assisted solvothermal method in isopropanol with the aid of glycerol. The roles of isopropanol, nitrate, glycerol, and the heating rate in the formation of the double shelled hollow spheres were systematically studied. The as-synthesized NiCo2O4 double shelled hollow spheres showed good sodium storage performance with reversible specific capacity of 511 mAh g-1 at 100 mA g-1. glycerol further anneaing microwave glycerol shrinkage NiCo2O4 DSHS NiCo2O4 yolk shell NiCo2O4 shell was tested as an anode material in a sodium ion battery, was found to exhibit a high reversible specific capacity of 511 mAh g-1 at 100 mA g-1, and deliver high capacity retention after 100 cycles. 1 Introduction Presently, due to increasing energy consumption, there is an increasing demand for energy storage materials. Lithium ion batteries (LIBs) offer high energy storage density, long cycling life, and excellent safety properties, thus dominating the market for portable electronic device power sources [ 1 ]. However, the depletion of lithium resources and the consequent high cost of lithium hinder the application of LIBs in several emerging areas, such as largescale grid energy storage [ 2 ]. Sodium, another Group I element, is much more abundant and has a much lower cost. As such, sodium ion batteries (SIBs), which have a charging/discharging mechanism similar to that of LIBs, are promising energy storage devices for the future and have received great research attention in the past few years [ 3 ]. Nevertheless, the energy storage performance of SIBs is significantly limited by a lack of suitable electrode materials. For example, while graphite is used as the anode material in most commercial LIBs, it is nearly electrochemically inactive with sodium due to the large ionic radius of Na? [ 4 ]. Although many other carbonaceous materials have been intensively investigated as anode materials for SIBs, their sodium storage capabilities are too low to meet the demands of practical applications. Transitional metal oxides have been widely investigated as substitutes for carbonaceous anode materials in LIBs [ 5 ]. In particular, ternary transition metal oxides such as NiCo2O4 are extremely attractive, due to their high theoretical storage capacities (e.g., 890 mAh g-1 for NiCo2O4 compared to 372 mAh g-1 for graphite) and superior electrical conductivity (2 orders higher than that of singlecomponent cobalt or nickel oxides) [ 6 ]. Theoretically, NiCo2O4 has equivalent storage capacities for both sodium and lithium. Recently, some work has been reported on the successful application of NiCo2O4 as an anode material for SIBs [ 7, 8 ]. However, due to the sluggish sodiation/desodiation reaction kinetics, as well as the large volume change during the charging/discharging process induced by the large ionic radius of Na?, the reported NiCo2O4 materials exhibit greatly inferior capacities for sodium storage. In order to increase the practical sodium storage capacity of this material, a new strategy to engineer robust nanostructured NiCo2O4 is urgently needed. One attractive avenue amongst the various approaches is the use of hollow multi-shelled spheres, due to their unique structural features [ 9–17 ]. Recently, microwave-assisted nanotechnology has attracted a great deal of research interest, due to the interest in green chemistry in both academia and industry. Microwaves heat the reactants directly via dielectric loss, rather than by heat convection as in the conventional heating method. This unique heating mechanism allows the use of microwaves to gr (...truncated)


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Xiong Zhang, Yanping Zhou, Bin Luo, Huacheng Zhu, Wei Chu, Kama Huang. Microwave-Assisted Synthesis of NiCo2O4 Double-Shelled Hollow Spheres for High-Performance Sodium Ion Batteries, Nano-Micro Letters, 2018, pp. 13, Volume 10, Issue 1, DOI: 10.1007/s40820-017-0164-2